Data Communication Principles
Working Principle
FSC-BT3431 Bluetooth BLE data transmission modules enable wireless communication between devices based on the BLE (Bluetooth Low Energy) protocol.
BLE : It adopts an event-driven low-power architecture and defines a “Service-Characteristic” model through the GATT protocol to realize intermittent small-data interaction (e.g., sensor data), making it suitable for IoT (Internet of Things) devices.
The module sends AT commands or transparent transmission data to the host device (mobile phone/MCU) via UART to complete connection establishment, data exchange, and status management.
As shown in the diagram, the Bluetooth module is used to replace the physical wires in full-duplex communication. A device such as a microcontroller unit (MCU) (on the left) sends data to the left-side Bluetooth module via its TXD pin. After the RXD pin of the left-side Bluetooth module receives the serial data, it automatically transmits the data via radio waves to the remote Bluetooth module (on the right). The right-side remote Bluetooth module then receives the over-the-air data and sends it to the local device (e.g., an MCU) on the right via its TXD pin.
MCU-to-Module Communication
This diagram shows a connection schematic of a main control MCU (Microcontroller Unit) and an FSC-BT3431 Bluetooth module. Command interaction between the main control and the Bluetooth module is realized through serial cross-connection, supporting wireless communication functions, which is applicable to scenarios such as IoT devices and remote control.
Serial Communication Interface : The transmitting end of the main MCU (MCU_TX) is cross-connected with the receiving end of the Bluetooth module (UART_RX), and the receiving end (MCU_RX) is similarly connected to the transmitting end of the Bluetooth module (UART_TX), forming a two-way data transmission channel.
Power Supply and GND : The Bluetooth module is connected to 3.3V via the VDD_3V3 pin and shares a common GND with the main MCU to ensure level compatibility and signal stability.
Module-to-Module Communication
Two FSC-BT3431 Bluetooth modules can establish a Bluetooth connection when powered on.
FSC-BT3431 module has master-slave device functions; the left module can be configured as a master device, and the right module as a slave device. The master device can send commands to realize Bluetooth scanning, connection establishment, data transmission, disconnection, etc. Among them, the device that actively initiates a Bluetooth connection is defined as a master device, and the device that receives a connection request is a slave device.
Module-to-Phone Communication
Why is an APP required on a mobile phone for Bluetooth connection and communication?
The native Bluetooth function of mobile phones only supports general scenarios, such as audio transmission and file transfer. Some Bluetooth peripheral devices can be connected through the mobile phone's built-in settings program, such as Bluetooth speakers, Bluetooth headsets, Bluetooth keyboards, Bluetooth mice, etc. When a Bluetooth peripheral device cannot be connected by the mobile phone's native settings program (for example, the Bluetooth module only supports SPP/GATT protocols), to connect such a module, it is generally necessary to install a specific mobile application on the mobile phone, such as the FeasyBlue application
Communication Application
Bluetooth Module side (FSC-BT3431) : It will continuously send broadcast data outward when powered on;
Mobile Phone side : It can search and obtain the broadcast packet of the FSC-BT3431 module through the FeasyBlue App , and initiate a MAC address/UUID connection request to the module side (FSC-BT3431), while obtaining all services and characteristics provided by the device.
After a successful connection, the Bluetooth module (FSC-BT3431) will pull high the connection status pin and report the connection status command (valid in command mode) to notify the host side of the successful Bluetooth connection;
Host side：Data can be sent to the remote (mobile phone side) Bluetooth via the serial port through the Bluetooth module, and the remote (mobile phone side) Bluetooth can also send data to the host .